Ore roasting furnace



June 1932- H. o. c. INGRAHAM 1,862,751

ORE ROASTING FURNACE Filed Dec. 31, 1929 2 Sheets-Sheet l INVENTOR Harold 0. 6. [nyra/mm IBYZVLX ATTORNEY June 14, 1932. H. o. c. YINGRAYHAM ORE ROASTING FURNAC E Filed Dec. 31, 1929 2 Sheets-Sheet yra/Mm Patented June 14, 1932 UNITED STATES PATENT OFFICE HAROLD O. C. INGRAHAM, OF GREENWICH, CONNECTICUT, ASSIGNOR TO GENERAL CHEMICAL COMIANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ORE ROASTING FURNACE Application filed December 31, 1929. Serial No. 417,660.

This invention relates to apparatus for roasting finely divided sulfide ores, flotation concentrates and the like, and more particularly to apparatus for roasting finely divided pyrite or other sulfide ores or flotation concentrates for the purpose of desulfurizing the same and producing sulfur dioxide for use in the manufacture of sulfuric acid.

The practice most generally followed at present in roasting sulfide fines, involves the use of mechanically operated multiple hearth furnace constructions, such as the well known Herreshoff and Wedge burners. Roasting furnaces of this type are effective, but their complicated structure and operation involve considerable initial and operating expense. Efforts have been made to provide other methods for roasting sulfide ores by which the ore might be roasted in a satisfactory manner, and at the same time to eliminate the employment of complicated and expensive apparatus. For this purpose the roasting of finely divided sulfide ores in gaseous suspension has been developed. In such instances the fines are either injected into a. roasting chamber in suspension in an oxidizing gas, or are showered downwardly into the roasting chamber wherein they encounter cross or counter-currents of gases which tend to hold the ore particles in suspension and en port the combustion thereof.

uspension roasting is particularly desirable when the ore is in a very finely divided state, such as flotation concentrates, and has the material advantage over the multiple hearth operation of lowering the production cost by eliminating the expensive apparatus necessary for the construction and operation of hearth burners. However, in the practice of suspension roasting, operating difficulties have been encountered which tend to offset the theoretical advantages over hearth roasting. One of the most serious difiiculties involved in the suspension roasting of sulfide fines is the objectionable formation of accretions or scar on the walls of the roasting chamber during the roasting opera tion. While in a particular stage of desulfurization, sulfide ores, and. iron pyrites particularly, have a tendency to readily adhere to the walls of the roasting chamber with the consequent building up of accretions thereon. Once the formation of accretions has been initiated, growth is rapid, and in a comparatively short time large masses of partially roasted and sintered material form on the roasting chamber walls, and tend to obstruct the passage through the burner and otherwise hinder the roasting operation. These difficulties often necessitated a shut down of the burner, and an interruption of the roasting process. In addition to the necessity of cessation of the roasting operation, there are the further disadvantages of excessive wear and tear on the apparatus on account of the falling of heavy lumps into the bottom of the burner shaft and the tendency of the lumps to clog the cinder discharge doors. Another objection is the incomplete desulfurization of the ore. The accretions contain considerable amounts of undesulfurized material which are confined within the accretions, and pass out of the burner with the cinder.

It is, therefore, an object of the present invention to provide an apparatus in which suspension roasting of sulfide fines may be effected without the foregoing disadvantages inherent in apparatus heretofore in use. The invention consists essentially in the provision of a mechanism in the roasting chamber by means of which accretions may be frequently scraped and cut away from the walls of the reaction chamber without interruption of the roasting process. The invention further contemplates a particular burner construction by means of which the scraping device, when not in use, may be withdrawn from the roasting zone, and thus protected from the injurious effects of the high temperatures prevailing therein. Another feature of the invention lies in the provision of means whereby the escape of gases from the roasting chamher is entirely prevented when the scraping device is withdrawn from the reaction chamher and in its normal inoperative position, and for reducing to a minimum the escape and loss of furnace gases when the scraper is being operated.

Other objects and features of novelty will be apparent from the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a sectional elevation of a shaft ore burner embodying the preferred form of the invention;

Fig. 2 is a plan view taken on the line 22 of Fig. 1;

Fig. 3 is an enlarged sectional elevation showing details;

Fig. 4 is a plan view of a portion of the scraper;

Fig. 5 is an elevation of that portion of the scraper shown in Fig. 4.

Referring to Fig. 1, the reference numeral indicates a shaft burner comprising the shell 11, constructed of suitable refractory material such as firebrick Or the like, which defines an elongated cylindrical roasting chamber 12. The top of the roasting chamber is formed by a crown member indicated generally at 13. The roasting chamber 12 is provided at its upper end with a feed inlet 14 in the center of the crown; a work hole 15 conveniently located to one side of the inlet 14; and near its lower end with cinder discharge openings 16, and a gas outlet 17 suitably connected to an exit gas main 18. The gas main 18 may be directed upwardly at a relatively high angle, for example approxi mately 60, and may advantageously be constructed with a comparatively large cross section to facilitate the deposition of dust particles from the exit gas stream and the return of the dust particles to the bottom of the roasting chamber. The work hole 15 and cinder discharge openings 16 are each provided with suitably constructed outwardly opening detachable closures 19 and 20.

A cylindrical extension 21, comprising a part of the crown member 13, projects downwardly .into the roasting chamber 12, and forms, in conjunction with the shell 11, an annular recess 22 into which a ringrshaped scraper 23 may be readily drawn. Extension 21 extends into the roasting chamber a sufficient distance so that the depth of the annular recess 22 is preferably somewhat more than twice the depth of the scraper 23. The purpose of this construction is to facilitate the withdrawal of the scraper from the roasting chamber when the scraper is not in use, and to thus protect it from the injurious effects of the high temperatures prevailing in the roastin chamber.

he greater portion of the weight of the projection 21 and the dome-shaped section 24 thereof is supported by the annular member 25, which may be of cast iron or other suitable material, the circular I-beam 26, and the several intermediate tie rods 27, the lower headed ends of which pass through holes bored at suitable intervals in the inner side of the upper horizontal flange of the I-beam. The I-bcam 26 and the tie rods 27 are embedded in the brick work of the extension 21 during the construction of the crown member. When the brick work has been completed, the annular ring member is lowered over the upper ends of the tie rods 27 into the position shown, and is securely held in place by means of the nuts threaded onto the upper ends of the tie rods 27. The member 25 is of sufficient width so that it projects outwardly over and obtains its support from the vertical walls of the shell.

The ore feed mechanism terminating in the feed inlet 14 is constructed as follows: The charging hopper 28, into which finely divided sulfide ore may be introduced in any suitable manner, is connected to the feed pipe 29 through the conduit 30 in which is mounted a screw conveyor 31 operated by the pulley 32 from a source of power not shown. The lower end of the feed pipe 29 extends into the mixing chamber 33. The pressure side of the blower 34 is connected to the mixing chamber 33 through a pipe 35. A dispersing cone 36 supported by a bracket 37 is placed in the feed inlet passage with the point thereof directly underneath the longitudinal axis of the feed pipe 29. The particular details of construction of the ore and gas mixing device are not an essential feature of the present invention. In the arrangement illustrated by way of example, the lower end of the feed pipe 29 projects into the mixing chamber 33 to a point just below the connection between the pi e and the mixing chamber 33. Thus,t e ore dropping out of the lower end of the feed pipe 29 is surrounded b air under a slight positive pressure whic in conjunction with the cone 36, serves to inject the ore in the roasting chamber as a suspension in air or whatever other oxidizing gas may be used, such as oxygen.

The weight of the mixing chamber 33. blower 34, hopper 28 and their'associated parts may be supported by suitable superstructure, not shown.

The scraper 23 is normally held in its up permost position in the recess 22, as shown in Figs. 1 and 3, by the counterweight 40 connected to the scraper through the chains 41, 42 and 43. The chains, consisting of uniform links, fit the chain sheaves 44, pass over the idler pulleys 45, and are connected to the scraper at three points equally spaced on the circumference thereof. The sheaves 44 and idlers 45 are fixed on their respective shafts which are journalled in bearings suitably supported by the superstructure, not shown.

The construction of the scraper 23 will be apparent from a consideration of Figs. 4 and 5. The scraper is preferably made of cast iron, and may be conveniently constructed in three sections, one complete section 46 being shown in Figs. 4 and 5. Bosses 47 are formed on either end of the inner side of section 46 to accommodate bolts 48 by means of which the several sections may be connected together to form a rigid unit. Guide bosses 49 are cast on the outer vertical surface of the ring at appropriate intervals, to facilitate movement of the scraper upwardly and downwardly in the roasting chamber and to prevent the jamming of the scraper against the walls. A series of outwardly projecting teeth 50 are formed on the lower edge of the ring for the purpose of cutting and scraping ofi accretions accumulating on the wall of the roasting chamber during the roasting process. Each section is provided approximately at its midpoint with a boss 51 adapted to receive an eyebolt 52 for securing the chains to the scraper ring. The size, shape, weight, and number of sections forming the scraper, and the number of points of suspension through which it is connected to the counterweight may be obviously varied according to the size and style of the furnace.

The manner of attaching the chains to the scraper, and the means for permitting the free movement of the chains through the crown of the burner are illustrated in Fig. 3. Tubes 55 are rigidly set into the brick work of the crown member directly over the annular recess 22. The circumferential spacing of the tubes on the crown member corresponds with that of the bosses 51 on the scraper. Tubes 55 project into the recess 22 a distance somewhat greater than the depth of the flanges of the cup-like member 56. The tubes are slightly larger in diameter than the links of the chains so that the latter may move freely therein. The cups 56, each provided with asbestos pads 57, are attached to the scraper by means of the eyebolts 52. As shown, the cups 56 are slightly larger in diameter than the tubes 55, so that the latter may telescope therein. When the scraper is in its uppermost position, the lower ends of the tubes 55 seat firmly in the asbestos pads 57, thereby forming a gas-tight closure on the lower ends 7 of tubes 55, and thus efiectively preventing the escape of gas from the burner.

A split ring 58 is threaded onto the upper end of each of the tubes 55. An upper washer-like section 59 is detachably secured to the ring 58 by means of two or more small screws 60. An asbestos diaphragm 61 may be thus clamped in place between the washer 59 and the body portion of the ring 58. The diaphragm 61 is slit in the center so as to permit the passage of the chain. This construction affords a maximum sealing around the links of the chain and tends to prevent the passage of any substantial quantities of gas through the tubes 55 when the scraper is being moved up and down in the roasting chamber for the purpose of cleaning the walls.

One or more work holes 62 may be constructed in shell 11 near its upper end as indicated in Fig. 1. Such work holes are provided with outwardly opening detachable closures 63, each of which includes a peep hole 64 to facilitate observation of the condition of the walls of the reaction chamber.

The operation of the invention in connection with the roasting of sulfide ore is substantially as follows: The furnace is first strongly preheated, for example by means of one or more oil burners inserted through a cinder discharge opening 16, until a temperature is obtained in the roasting chamber 12 substantially above the ignition point of the particular sulfide ore to be roasted. If iron pyrites is being employed, the temperature of the roasting chamber should be initially about 600 C. to 800 C. During the preheating operation, the work hole 15 should be open to permit the escape of the products of combustion. Finely divided iron pyrites, or any other sulfide ore, preferably dried until the moisture content is not greater than about 3%, and of a particle size of approximately 60 mesh, is then fed into the hopper 28 in any suitable manner. From the hopper the fines are, continuously supplied to the feed pipe 29 by the screw conveyor 31. Air may be most economically employed as an oxidizing gas, and is supplied to the mixing chamber 33 by means of the blower 34. The air may or may not be preheated. The

amount of air introduced will depend upon the amount of sulfur in the fines ore to be desulfurized, the desired concentration of sulfur dioxide in the exit gases in the conduit 18, and other features evident to those skilled in the art. The regulation of the air supply may be effected in any well known manner.

As the particular method of roasting the ore forms no part of the present invention, it will be only necessary to state that a mixture of finely divided sulfide ore in a suspension of a combustion supporting gas is fed into the roasting chamber 12. As the roasting chamber has been previously preheated to the temperature above that necessary for the ignition of the sulfide ore, and as the roasting of such sulfide ores under these conditions is strongly exothermic, it will be understood that after the oxidation reaction has been once initiated, it will proceed without the addition of external heat.

As the reaction in the roasting chamber 12 proceeds, a sintering of ore particles near the burner walls takes place, with the result that accretions tend to form on the walls of the reaction chamber. At appropriate intervals, depending upon the particular operating conditions, the scraper may be lowered out of the annular recess 22, and dropped downwardly through the length of the reaction chamber for the purpose of removing any accretions which may have formed on the walls thereof. The movement of the scraper may be efi'ected manually, or by means of a suitable motor operating through the shaft on which the chain sheaves 44 are mounted. The vertical distance through which the scraper may be moved is dependent upon the length of the chains. However, it will be usually unnecessary to provide for the movement of the scraper through the reaction chamber for more than two thirds of its length as the scarring will ordinarily take place almost entirely in the upper part of the chamber. When the scra er is in its uppermost position as shown in ig. 1, the passages through the tubes are completely closed off by the asbestos pads 57, thereby preventing the escape of gas from the reaction chamber. During the movement of the scraper through the reaction chamber, the escape of Y gases through the tubes 55 is reduced to a minimum by diaphragm 61.

It is thus apparent that the invention provides an apparatus by means of which accretions forming on the walls of the roasting chamber may be mechanically removed at frequent intervals without interruption of the roasting process. It should be understood that the invention is applicable to operations other than the roasting of ore in which similar difficulties of scar or clinker formation are encountered.

1. An ore roasting furnace comprising a shell defining a vertically disposed cylindrical roasting chamber, a crown member closing the top of the roasting chamber, a cylindrical member associated with the crown projecting into the roasting chamber and forming with the walls of the chamber an annular recess, a ring-shaped wall cleaning device normally positioned in the recess, and means for raising and lowering the device to scrape the walls of the chamber.

2. An ore roasting furnace comprising a shell defining a c lindrical roasting chamber, a crown member closing the top of the roasting chamber, means for feeding into the roasting chamber a suspension of finely divided ore in a combustion supporting gas, a cylindrical member associated with the crown projecting into the roasting chamber and forming with the walls of the chamber an annular recess, a ring-shaped wall cleaning device normally positioned in the recess, and means for moving the device out of the recess and through the roasting chamber in contact with the walls thereof.

3. A furnace comprising a shell defining a reaction chamber, a crown closing one end of the chamber, a member associated with the crown projecting into the chamber and forming with the walls of the chamber a recess, a wall cleaning device normally positioned in the recess, and means for moving the device out of said recess and along the chamber walls.

4. A furnace comprising a shell defining a reaction chamber, a crown closing one en of the chamber, means for feeding into the chamber a suspension of finely divided combustible material in a combustion supporting 5. A furnace comprising a shell defining a vertically disposed reaction chamber, a crown closing the top of the chamber, a member associated with the crown projecting into the chamber and forming with the walls of the chamber a recess, a wall cleaning device normally positioned in the recess, and means for raising and lowering the device to scrape the walls of the chamber.

6. A furnace comprising a shell defining a cylindrical reaction chamber, a crown member closing the top of the chamber, a cylindrical member associated with the crown projecting into the chamber and forming with the walls of the chamber an annular recess, a ring-shaped wall cleaning device normally positioned in the recess, and means for moving the device out of the recess and through the chamber in contact with the walls thereof.

7. A furnace comprising a shell defining a reaction chamber, a crown member closing one end of the reaction chamber, means associated with the crown member for feeding into the reaction chamber a suspension of finely divided combustible material in a combustion supporting gas, a wall cleaning device normally positioned adjacent the crown member and means for moving the device through the chamber in contact with the walls thereof.

8. An ore roasting furnace comprisin a shell defining a vertically disposed roastin chamber, a crown member closing the top 0 the roasting chamber, means associated with the crown member for feeding into the roasting chamber a suspension of finely divided ore in a combustion supporting gas, a wall cleaning device within the roasting chamber and normall positioned adjacent the crown member, and means for operating the cleaning device including flexible members and an attached counterweight.

.9. An ore roasting furnace comprising a shell defining a vertically disposed cylindrical roasting chamber, a crown member closing the top of the roasting chamber, means associated with the crown member for feeding into the roasting chamber a suspension of finely divided ore in a combustion supporting gas, a ring-shaped wall cleaning device in the reaction chamber, means for operating the cleaning device including chains attached thereto and a counterweight secured to the chains, sleeve members set into the crown member to provide for the passage of the chains through the crown member, and means in the sleeves tending to prevent the passage of gas therethrough when the cleaning device is being moved through the chamber.

10. An ore roasting'furnace comprising a shell defining a vertically disposed cylindrical roasting chamber, a crown member closing the top of the roasting chamber, means associated with the crown member for feeding into the roasting chamber a suspension of finely divided ore in a combustion supporting gas, a ring-shaped wall cleaning device in the roasting chamber, means for operating the cleaning device including chains attached thereto and a counterweight secured to the chains, sleeve members set into the crown member to provide for the passage of the chains through the crown member, means in the sleeves tending to prevent the passage of gas therethrough when the cleaning device is being moved through the chamber, and means associated with the cleaning device and the sleeves for preventing the passage of gas through the sleeves when the cleaning device is in its uppermost position.

11. An ore roasting furnace comprising a shell defining a vertically disposed cylindrical roasting chamber, a crown member closing the top of the roasting chamber having a cylindrical portion projecting into the roasting chamber and forming with the walls thereof an annular recess, a ring-shaped wall cleaning device normally positioned in the recess, means for supporting and operating the cleaning device including chains attached thereto and a counterweight secured to the chains, sleeve members set into the crown member to provide for the passage of the chains therethrough, and means in the sleeves tending to prevent the passage of gas through the sleeves when the cleaning device is being moved through the chamber.

12. An ore roasting furnace comprising a shell defining a vertically disposed cylindrical roasting chamber, a crown member for closing the top of the roasting chamber having a cylindrical portion projecting into the roasting chamber and forming with the walls thereof an annular recess, a ringshaped wall cleaning device normally positioned in the recess, means for supporting and operating said cleaning device including chains attached thereto and a counterweight secured to the chains, sleeve members set into the crown member to provide for the passage of the chains therethrough, means in the sleeves tending to prevent the passage of gas through the sleeves when the cleaning device is being moved through the chamber, means associated with the cleaning device and sleeves for preventing the passage of gas through the sleeves when the cleaning device is in its uppermost position.

13. A furnace comprising a reaction chamber, means for feeding into the chamber a suspension of finely divided combustible material in a combustion supporting gas, a

wall cleaning device in said chamber and means for moving the device through the chamber in contact with the walls thereof.

14. An ore roasting furnace comprising a shell defining a reaction chamber, a crown member closing one end of the reaction chamber, a wall-cleaning device in said chamber, and means for moving said device through the chamber in contact with the walls thereof.

15. An ore roasting furnace comprising a shell and a crown member defining a vertically disposed reaction chamber, a wallcleaning device adapted to move vertically in the chamber adjacent the walls thereof, and means for raising and lowering said wallcleaning device.

16. An ore roasting furnace comprising a shell defining a reaction chamber, a crown closing one end of the chamber, a member associated with the crown projecting into the chamber and forming with the walls of the chamber a recess, a wall-cleaning device normally positioned in the recess, and means for moving the device out of said recess and along the chamber walls.

In witness whereof I hereunto set my hand.

HAROLD O. C. IN GRAHAM. 

